CSAS Oral Student Competition: PHD Session
The objective was to evaluate short-chain fatty acid (SCFA) absorption and permeability of the gastrointestinal tract (GIT) of heifers infused either with Ca-gluconate or Ca-butyrate. Thirty-two ruminally cannulated beef heifers were fed a common diet (forage-to-concentrate ratio of 50:50) for 28 d and once daily infused with water (ruminal infusion; control), Ca-gluconate embedded in a fat matrix (ruminal infusion; 0.192% BW), unprotected Ca-gluconate (abomasal infusion; 0.077% of BW), and unprotected Ca-butyrate (abomasal infusion; 0.029% BW). Treatments were designed to provide the same amount of butyrate to the small intestine. DMI was restricted to 95% of voluntary DMI on d 8 and was recorded until heifers were slaughtered on d 28. Rumen, jejunum, and colon tissues were collected to determine the rate and pathway of SCFA transport, and for measurement of permeability.14C-acetate and 3H-butyrate absorption across the ruminal and colonic epithelium was measured with no inhibition and under maximal inhibition. Permeability was assessed for the rumen, jejunum and colon using mucosal-to-serosal flux of 14C-mannitol. Initial and final BW were not different (P > 0.60) averaging 388 ± 5.5 kg and 409 ± 6.6 kg, respectively. DMI was not affected by treatment averaging 7.7 kg/d (P = 0.77). Treatment did not affect the flux of acetate or butyrate across the ruminal or colonic epithelium (P > 0.33), but flux rates of SCFA were numerically greater across the ruminal epithelium. Moreover, approximately 50% of the ruminal acetate was transported via bicarbonate-dependent mechanisms. Mannitol flux was not affected by treatment (P > 0.29) and was numerically lower in the rumen and colon than in the jejunum, supporting previous research evaluating permeability across the GIT. According to this experiment, provision of Ca-butyrate or Ca-gluconate in an attempt to increase intestinal butyrate supply does not impact SCFA absorption or permeability of the rumen, jejunum, or colon.